Perhaps you should try some spelling variations:
thien van » thi van
cua triet » cua viet, va triet
thu sach » tu sach, thuat sach, thuoc sach
dang hai » dang khai, hang hai, dung hai
van dang » van dong, van dung, van nang
nuoc van » nuoc va, nuoc san, luoc van
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
su triet » su viet, su tien, ve triet
van cac » van hac, van cau, van bac
y nang » ky nang, ly nang, may nang
v nang » va nang, vu nang, van nang
x hoi » xa hoi, o hoi, x ho

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ((y nang) OR (v nang)) x hoi. thien van cac nuoc van dang hai ((cua triet) or (su triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ((y nang) OR (v nang)) x hoi. thien van cac nuoc van dang hai ((cua triet) OR (su triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ((y nang) OR (v nang)) x hoi. thien van cac nuoc van dang hai ((cua triet) or (su triet))".
• Adding a wildcard symbol may retrieve word variants: thu sach ((y nang) OR (v nang)) x hoi. thien van cac nuoc van dang hai ((cua triet) or (su triet))*.